VOA慢速英语:US Company Developing Space-Based Plane Tracking

constellation – n. a group of people or things that are similar in some way

highlight – v. to make or try to make people notice or be aware of someone or something;  to direct attention to someone or something

monitor – v. to watch, observe, listen to, or check something for a special purpose over a period of time

range – n. the distance over which someone or something can see, hear, or reach someone or something else

surveillance – n. the act of carefully watching someone or something especially in order to prevent or detect a crime

unique – adj. used to say that something or someone is unlike anything or anyone else